1. Field of the Invention
The invention relates generally to string sets of series-connected, decorative, incandescent lamps. More particularly, the invention relates to a string set construction wherein two unshunted lamps and the two wires connecting the lamps to a plug act as a fuse for the string set.
2. Description of the Prior Art
In the past, most string sets of series-connected decorative incandescent lamps have been made of either 18-gauge wire for outdoor use or 20-gauge wire for indoor use. Unfused string sets made of smaller conductor wires would not be protected by the conventional 15- and 20-ampere branch circuit fuses and circuit breakers. In other words, if an unfused indoor string set with a wire size smaller than 20 gauge encountered an electrical problem, the 15-or 20-ampere fuse or breaker would not open the circuit. This is so because the current flowing through the smaller diameter conductor would not be sufficient to trip the circuit breaker or blow the fuse even when there is a problem in the set. Accordingly, the heat buildup in the string set of the smaller gauge wire would continue to a point where it might ignite the string set insulation or anything in the surrounding area before any fuse would blow or breaker trip.
Although the economies of using string sets of smaller gauge wire are great, they should not be used without short circuit protection. Any short circuit protection designed into a string set should have the qualities of being able to utilize standard parts such as lamp sockets, wires and insulation which are presently used in the string set industry. Furthermore, any short circuit protective device should also have the quality of being able to blend in with all the other lamps and sockets of the string set inasmuch as these sets are primarily used for decorative purposes.